Geographic Range

Moon jellies inhabit the coastal regions of the Pacific Ocean from San Diego, California, to Prince William Sound, Alaska. Though Aurelia labiata has been identified solely in this Eastern region of the Pacific Ocean, its close relative A. aurita is a cosmopolitan species that is ecountered in coastal waters around the world. Confusion in identifying the two species may distort the true range of the moon jellies. (Gershwin, 2001)

Habitat

Moon jellies float near the surface in warm nearshore waters and are especially prevalent in bays and harbors, such as the Monterey Bay. Though common in coastal regions, moon jellies have been referred to as pelagic, or living in the open waters of the ocean. An extremely close relative to A. labiata, A. aurita can survive in waters ranging from -6 to 31 degrees Celsius. It is very likely that A. labiata tolerates similar temperature ranges. (Purcell, et al., 2000; Robel, 2001; Rodriguez, 1996)

Physical Description

The translucent, moonlike bell that is characteristic of Aurelia labiata has earned moon jellies their common name. They do not have the long trailing tentacles that people usually associate with jellyfish. Instead, they have a fine fringe lining the bell margin. The body form of A. labiata is distinguished from close relatives in the genus Aurelia by an enlarged, fleshy manubrium, four oral arms protruding from the base of the manubrium, planulae (ciliated fertilized egg) brooding on the manubrium, and secondary scalloping of the bell margin between rhopalia, forming 16 notches. Aurelia labiata ranges from 100 mm to 450 mm. Bells of juveniles and young adults are translucent, and with maturity they turn milky white, sometimes with a pink, purple, peach, or blue tint. (Monterey Bay Aquarium Foundation, 2003; Robel, 2001)

Aurelia labiata can easily be divided into three geographical morphotypes. The southernmost form, found in California from San Diego to Marina del Ray, has a manubrium that is a wide, rounded frill. The radial canals range in number, depending on age. The oral arms are typically straight. Planulae range in color from white to bright orange, and the bells are colorless to milky white. Male gonads are dark purple, and female gonads are pale pink. Southern moon jellies grow to a maximum of 35 cm.

The central form inhabits coastal waters from Santa Barbara, California, to Newport, Oregon. Abundant in late summer, central moon jellies have an elongated manubrium that is rectangular and tapering. The radial canals are very numerous, and the oral arms are straight or bent counter-clockwise. The planulae are lavender, and medusae found in Monterey, California, are usually purple, while those found in Santa Barbara are often pale pink. Male gonads are dark purple, and female gonads are brown. Individuals of the central form of A. labiata have been recorded as high as 45 cm.

The northernmost form, ranging from Puget Sound, Washington, to Prince William Sound, Alaska, have a pyramidal manubrium. The many parallel radial canals of adults give the bell a lacy appearance. The oral arms are generally straight, and the planulae are found in variable colors. The bells are peach or whitish, male gonads are dark purple, and female gonads pale brown. Northern moon jellies range in size from 14-29 cm. (Gershwin, 2001)

Development

Male and female medusa spawn into the sea where the eggs are fertilized. The fertilized egg is called a planula, a cilliated organism that is elliptical and elongated. The planulae are brooded on the manubrium of Aurelia labiata. They are shaken off and attach to a substrate, usually hanging upside-down from the underside of docks, mussel shells, or rocks. There they transform into a polyp 2-3 mm in height, with an oral disk 1-2 mm in diameter. Polyps range in color from whitish to pale pink and orange. Polyps attached to a substrate asexually reproduce by side budding, stolon budding, or podocyst formation.

Eventually the polyp strobilates, meaning that it transforms into a stack of several organisms. In moon jellies, the strobila are both monodisk (produced one at a time) and polydisk (several disks produced), with more than 20 developing ephyrae (free-swimming, immature medusae). Their color varies with location (cinnamon in Southern California and tan in Monterey). The strobilation time lasts for about 7 days, and the ephyrae are released. Typical ephyrae are 2-3 mm when released, with 8 marginal arms and nematocysts (stinging cells) on the exumbrellar surface. The ephyrae swim about until they develop into mature medusa form. (Gershwin, 2001)

Reproduction

Moon jellies reproduce using internal fertilization. The gonads are one of the most recognizable characteristics of the animal. They are horseshoe shaped organs with deep coloration that can be seen in the center of the bell. In the mating season, males are seen with sperm filaments attached to their oral arms. Sperm is carried to the gastric pouch of the female by cilliary currents. Females hold the fertilized eggs, which appear as grey clumps, on the manubrium. (Gershwin, 2001; Robel, 2001)

Only recently has Aurelia labiata been redefined as a species unique to its close relative Aurelia aurita, the saucer jelly. Information on reproductive behavior or A. labiata is not available at this time. Aurelia aurita is known to reach sexual maturity in the spring and summer. In these seasons much of the organism's energy is devoted to repoduction. As the jellies live in close aggregations, complex mating rituals do not exist, males simply release their sperm filaments during the period of sexual maturity, which are carried to the female gonads by ciliary currents. (Gershwin, 2001; Hickman, et al., 2003; Rodriguez, 1996)

The zygotes of Aurelia labiata, called planulae, are brooded on the jelly's manubrium. In the Southern form, this takes place in a reticulating pattern on the frills. In the central form, the planulae are brooded in tear-drop shape clumps on the base or shelves of the manubrium. Northernmost moon jellies brood planulae at the base or shelves of the manubrium as well. Planulae are eventually shaken off and continue their development after attaching to a substrate. (Gershwin, 2001)

Parental Investment

no parental involvement

pre-fertilization

provisioning

pre-hatching/birth

provisioning

female

protecting

female

Lifespan/Longevity

Aurelia labiata polyps usually strobilate early in spring, and the medusae mature very quickly, spawn, and die by midsummer or early fall. In certain places, the medusae population is present year-round. (Gershwin, 2001)

Typical lifespanStatus: wild

1 (high) years

Behavior

Moon jellies appear in aggregations of hundreds to millions of individuals. These aggregations are widely studied in Prince William Sound, Alaska, suggesting that the jellies get stuck in flow features of the water column, forming the groups. Reduced swimming due to collisions amongst the medusae in crowded areas is believed to assist in maintenance of the aggregations. Possible advantages of aggregating behavior includes increased fertilization success, the ability to stay near shore where zooplankton and planula settling sites are more abundant, and reduced predation. (Purcell, et al., 2000)

Communication and Perception

Little is known about communication between moon jellies. They are relatively primitive animals, so it is likely that if communication between individuals exists at all, it is in a very simple form. Research in this area is lacking.

Food Habits

Aurelia labiata feeds on small zooplankton such as molluscs, crustaceans, fish eggs, and other small jellies. In a gut sampling study, moon jellies primarily selected for crustacean prey. Thorough research on the specific dietary habits is missing from scientific discourse, but the close relative species Aurelia aurita has a diet of plankton organisms as well. Aurelia aurita has a diet dominated by whatever prey type is abundant, adjusting to the availability of given food types.

The plankton is caught on the mucus lining the bell of the jelly. It is moved by ciliary action to the bell margin, where the short fringe of tentacles helps funnel the food into the manubrium and the four horseshoe-shaped stomach pouches at the top center of the bell. (Monterey Bay Aquarium Foundation, 2003; Purcell, 2002; Robel, 2001)

Ecosystem Roles

Aurelia labiata is an important consumer of marine zooplankton. They overlap spacially and temporally with important commercial fish, such as the walleye pollock in the Prince William Sound. They potentially compete with these fish species, which also feed on marine zooplankton. Studies have yet to prove that large jellyfish, especially A. labiata, significantly threaten the livelihood of zooplanktivorous fish, but they have shown that their diets and habitats overlap. This could lead to competition for resources. (Purcell, 2002)

Economic Importance for Humans: Positive

Aurelia labiata adapt readily to an aquarium environment and can thrive at a variety of temperatures. In addition, their translucent coloring, moon-shaped bell, and pulsating method of swim make them very beautiful. It is relatively easy to establish polyps and breed the jellies in captivity. For these reasons, moon jellies are some of the most displayed jellyfish at public aquariums. Distributors of jellyfish have opened a new market among consumers who want moon jelly tanks in their homes. Aurelia labiata is emerging as an important commodity in the pet trade, and serves as an attraction at aquariums worldwide. (Gershwin, 2001; Robel, 2001)

Economic Importance for Humans: Negative

There is concern, but no causal evidence as of yet, that the blooming populations of moon jellies will dominate consumption of zooplankton food resources and outcompete commercial fish that also depend on the resource. Further studies will be necessary to determine if this concern is valid. (Purcell, 2002)

Conservation Status

Other Comments

In classifying different species of jellyfish, twentieth century taxonomists tended to classify any flat, whitish medusa with four horseshoe-shaped gonads as Aurelia aurita. Many morphological differences have thus been ignored, and false conclusions about species such as Aurelia labiata have been made. Rigorous research by Lisa-Ann Gershwin on the anatomical species has resurrected Aurelia labiata as a species unique from its close relatives. For decades the individuality of the species was ignored. (Gershwin, 2001)

Contributors

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.